C-Forum

Reading Colin's pump thread, someone mentioned not using fuses.

Anybody running a 12 volt pump in their boat without fuses try this.

Get a lead acid 12 volt battery and run a 16 gage or smaller wire from + to -. Yeah short that puppy out. ( some of the newer batteries, Lithium Ion in particular, may burn up or explode.)

Watch the wire get red hot and melt off the insulation before the copper melts and opens the short.

Imagine that wire melting through your boat. Or your wetsuit!

If I decide to run a 12 volt pump I'll have a fuse right after the battery. For Sure.

Nope, I'm no wizard but I did burn up a truck some years back doing something similar.

Tommy

hmmmm...maybe I can put an extra switch on my saddle and run some extra wire inside my saddle for those cold days...heated seats

Heated seats, now you're talking.

About about a heated paddle shaft and grip?

Tommy, my dual 1250 pumps, off a 12 v, no fuse have been working a year without fail ever since you set me straight on the circular wiring thing I had going on. Now ya tell me I need a fuse?

Being electrically challenged, please tell what kind of fuse do I need and where and on what wire does it go? Thanks

Been running no fuses on three different bilge rigs (on 1000gph to 1600 gph pumps) for over four seasons without any problems... You do not need them. Especially on a 40$ pump that can be replaced...

Heidi,
Running two 1250s together a 10 amp slo blow fuse ought to work. I'd put it in between the + terminal of your battery and the wire you conect up to the + terminal now.

Sbrassfield,
You are right. It will work fine without the fuse and there will be no danger so long as your pump or wiring does not short.
For the same reason, you don't need circuit breakers in your house either. No shorts no problem.


Tommy

four seasons several boats - no issues - yet.

I use SLA - If you use Lion or NiCad etc - Better use fuses.

Keep wires protected - I run them through the saddle - under gunnels or use a wire conduit. Protect them and the probability of issues is low. A simple broken connection like a wire coming loose will not cause a problem but a true short (bridging + & - ) will be a problem. Typically worn through insulation from abrasion or a cut through + & - permitting a connection will cause this. Fresh water will not conduct enough to be a problem.

I quit even putting the battery in a box to save weight - but use a waterproof switch.

Who needs shorts But Rubber soles are a good idea Might even consider neoprene knee pads...

Having setup several OC1's with pumps, there is no reason not to use a fuse. , 12 volt 4 amp. fast blow one note.. Its a good idea to run the wireing as follows: positive terminal on the batt. ,through a fuse, then to the pump. , then out of the pump to the on off switch and finally form the switch to the neg terminal on the batt. . This configuration causes a 12 volt voltage drop across the pump before going to the switch.

ClassFive Boats wrote:then out of the pump to the on off switch and finally form the switch to the neg terminal on the batt. . This configuration causes a 12 volt voltage drop across the pump before going to the switch.

So if I am reading this right your putting the switch between the negative terminal of the battery and the negative wire to the pump.

Doesn't make sense to me with what I know about wiring.

Think of your circuit panel in your house. All the neutral white wires (negative in our case) are effectively joined together in the panel thru a common bus bar.

The circuit breaker (switch in our case) in on the hot black wire ( positive wire in our case).

Every piece of 12 volt dc electronics that I know of have the switch somewhere on the positive side of the circuit.

I think what he is saying is that if the switch is after the load , then there is less power in the circuit going thru the switch, therefore less of a chance of switch failure. The lighting circuits in your house should be wired like this,it is why they always tell you to turn off the breaker(the positive feed) before working on a light or outlet. I'm not an electrician, but thats how I understand it. Any electricians feel free to comment.

OK ... I just looked at my electrical code manual (Ontario, Canada) which has lots of wiring diagrams for just about anything.

In the case of a house and say a light.

The breaker is our fuse.

The switch goes between the breaker and the light on the black hot (positive) side. The other side of the light goes to the white neutral (negative) side. All the neutrals in the house are actually tied together and are effectively the same as a ground.

They tell you to turn the power off so you don't get electricuted to avoid lawsuits.

Maybe I am not thinking outside of the box here and that I am not getting this switch after the load thing.

Hey kids,
The switch just needs to be in series with the pump. Doesn't matter if it's on the + or - side.
Since there is only one load and no ground there really is no common.
The current is constant throughout the circuit.
When the switch opens the voltage drop goes away. The arc as the contacts open will be the same whichever side you switch. The arc is what burns the switch contacts. Unless you are lucky or your switch is undersized your switch will have a mechanical failure before the contacts burn out.

Craig if your house is wired with the neutrals switched better warn any electrician working there! Typicaly the hot is switched and the neutral is not. The switch will work in either case but the sparky might get whacked if he isn't carefull!

Tommy
(Electrician)

told you I wasnt an electrician, so I only understood this partially. This part I get ; Battery (pos) -fuse - switch-pump-return to battery(neg) correct?

Craig,
That will work fine.